The development and introduction of new refrigerants and their associated oils in recent years has required changes to compressor designs that are not yet obsolete in order to provide satisfactory performance. Basically, the use of new synthetic oil with the HFC refrigerants mandates compressor redesigns for improved lubrication during transient conditions such as those associated with start up. The inherent characteristics of the new synthetic oils cause the adsorption and desorption of refrigerants at vastly different rates than the mineral oils. When the refrigerant flashes out of the oil, standard compressor designs maintain the resulting increased pressure in the oil sump. This results in higher than normal sump pressures during these transient conditions resulting in performance degradation of the bearing and lubrication system. This was partially addressed in commonly assigned U.S. Pat. No. 5,211,542 which limits the pressure differential between the suction plenum and the oil sump. Additionally, the new refrigerants do not transport oil as well as conventional refrigerants.